Rotary limit switch



April 29, 1969 NEWMAN ETAI- 3,441,691

ROTARY LIMIT SWITCH Filed June 9, i967 Sfiazz/ey 225mg. gird??? fl/mk a zfer 11/ s ya United States Patent Oflice 3,441,691 Patented Apr. 29, 1969 3,441,691 ROTARY LIMIT SWITCH Stanley F. Newman, Troy, Gerald H. Dion, Warren, and

Walter Cwycyshyn, Detroit, Mich., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed June 9, 1967, Ser. No. 645,058 Int. Cl. Hlh 3/16 US. Cl. 200-47 2 Claims ABSTRACT OF THE DISCLOSURE of movement.

This invention relates to limit switches and more particularly to a limit switch assembly utilizing a circular cam follower to selectively position magnetic material near a reed switch to energize or deenergize electrical circuits as desired.

In certain types of machinery, it is important to energize and deenergize electrical circuits at a point in time corresponding to the amount of movement of a linear type generated in a portion of the machine. It is important in limit switch actuation that the switching be done very positively and that it occur at a precise point in the linear movement of the object. At the same time, machinery is generally constructed of electrically conductive material and, therefore, it is desirable to have electrical apparatus associated therewith completely insulated from the machine itself. It is also desirable in a switching function to utilize components for switching that will not readily deteriorate due to the environment in which they operate and which, consequently, are substantially maintenance free.

It is an object of the present invention to provide an improved limit switch assembly that is capable of sensing linear movement either at its extremes or at any point intermediate the extremes.

It is another object of the present invention to provide an improved limit switch utilizing sealed reed switches that are magnetically operated and which involves very little contact movement in undesirable environments.

It is still another object of the present invention to provide an improved limit switch assembly for use with machinery having linearly moving parts which allows the switching of associated circuitry at a predetermined point in travel of a linearly moving part of the machine while maintaining the machine completely insulated from electrical circuitry.

Further objects and advantages of the present invention will be apparent from the following description, references being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

IN THE DRAWINGS FIGURE 1 is a perspective view of the limit switch assembly which is the subject of the present invention;

FIGURE 2 is a sectional view taken along line 2-2 of FIGURE I.

Referring to FIGURE 1, a switch support means is carried in a fixed relationship with respect to movable members 12 and 14 of a machine, not shown. Members 12 and 14 move in unison and have cam surfaces 16 and 18 respectively formed thereon.

A rotary member 20 is substantially circular in shape and is journalled in support 10 by shaft 22. Bearings 24 are carried on shaft 22 in order to facilitate the rotational movement of member 20. Rollers 26, 28, and 32 are carried on one side of rotary member 20 and near the periphery thereof. Rollers 26 through 32 extend beyond the periphery of member 20 in a manner allowing selective engagement thereof with cam surfaces 16. Similarly, rollers 34, 36, 38 and 40 are carried on an opposite face of rotary member 20 and likewise extend past the periphery thereof to selectively engage cam surface 18. The sets of rollers on either side of member 20 are so radially positioned that a roller is always in contact with cam surface 16 and a roller on an opposite side of cam member 20 is always in contact with cam surface 18. This provides the stability that is characteristic of the present invention.

Referring to FIGURE 2, reed switches 42 and 44 are shown as carried by support 10 in a fixed manner with respect to rotary member 20. Magnetic material designated by numerals 46 and 48 is carried by rotary member 20 and is moved into a position adjacent reed switches 42 and 44 at predetermined times during rotation of member 20 as determined by the relative position of the rollers on cam surfaces 16 and 18. In this manner, the position of the rollers along cam surfaces 16 and 18 can be sensed and converted into an electrical function by the appr0- priate opening or closing of either reed switches 42 and 44. It is obvious that any number of reed switches and magnetic materials could be positioned on the support 10 on rotary member 20 as desired in a given installation to provide almost limitless combinations of electrical functions.

It is quite obvious that in the present invention it is impossible to accidentally operate the electric switch and the switches cannot be tied in the operated position. In addition, unlimited overtravel of the movable members 12 and 14 is made possible without damage to the switch.

Another important feature of the present invention is that the bearing shaft and other moving conductive portions of the mechanism can be completely isolated from the electric contacts and wiring. The switch also enables the use of reed switches which operate in a controlled environment but which enables this advantageous use without the normal involvement of springs. Therefore, the present invention teaches a limit switch assembly which is very positive in its operation and which is virtually maintenance proof. Consequently, the present limit switch assembly is not beset by the normal problems associated with a limit switch operating in the environment in which a limit switch is expected to function.

While the embodiment of the present invention, as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is:

1. A limit switch assembly for sensing extremes of linear movement, said limit switch assembly comprising: switch support means carried in fixed relationship with respect to an object whose linear motion is to be sensed; switch positioning means rotatably carried by said switch support means; switch actuating means carried by said switch positioning means; reed switch means carried by said switch support means and positioned in an electrical circuit energizable when an object whose linear motion is to be sensed is at an extreme of movement; and switch operating means carried by an object whose linear movement is to be sensed and engaging said switch positioning means during every portion of its linear movement, said switch operating means rotating said switch positioning means at predetermined points in the linear movement of the object whose movement is being sensed to move said switch actuating means in alignment with said reed switch means to selectively energize and deenergize electrical circuits.

2. A limit switch assembly for sensing the position of an object being linearly moved, said limit switch assembly comprising: a support member being fixed with respect to an object capable of being linearly moved; a substantially circular member being centrally journalled on said support member and including rollers peripherally carried on said circular member; magnetic material carried by said substantially circular member; reed switches carried by said support member in juxtaposed relation to said circular member; and cam means carried by the object capable of linear movement in engagement with said rollers, said cam means engaging said rollers during every References Cited UNITED STATES PATENTS 10/1962 Clare 335-206 5/1966 Briggs 335205 ROBERT K. SCI-IAEFER, Primary Examiner.

D. SMITH, JR., Assistant Examiner.

US. Cl. X.R. 

